Quran 49:3 from Surah Al-Hujuraat on Divine Marvels.
إِنَّ ٱلَّذِينَ يَغُضُّونَ أَصۡوَٰتَهُمۡ عِندَ رَسُولِ ٱللَّهِ أُوْلَٰٓئِكَ ٱلَّذِينَ ٱمۡتَحَنَ ٱللَّهُ قُلُوبَهُمۡ لِلتَّقۡوَىٰۚ لَهُم مَّغۡفِرَةٞ وَأَجۡرٌ عَظِيمٌ
English translation: Indeed those who lower their voices (in) presence (of the) Messenger of Allah (of the) Messenger of Allah those (are) the ones Allah has tested Allah has tested their hearts for righteousness For them (is) forgiveness and a reward great
Transliteration: inna alladhina yaghudduna aswatahum inda rasuli al-lahi ulaika alladhina im'tahana al-lahu qulubahum lilttaqwa lahum maghfiratun wa-ajrun azimun